A New Fixed Axis-Invariant Based Calibration Approach to Improve Absolute Positioning Accuracy of Manipulators

This paper studies the calibration of industrial robots. Aiming at the problems of cumbersome industrial robot modeling and poor calibration effects, this paper proposes a new calibration method for determining the DH frame and DH parameters of industrial robots by measuring first and modeling afterwards. Firstly, the theory of Fixed Axis-Invariant is proposed, the Axis-Invariant is determined based on dual-vectors, and the origin of Fixed Axis-Invariant is determined by intersection obtained through the projection from one measuring point to the Axis-Invariant. Secondly, a method for solving the D-H frame and D-H parameters of industrial robots based on Fixed Axis-Invariant is proposed. Then, combined with laser tracker and industrial robot control software for secondary development, the developed software can be used to automatically measure and obtain the D-H frame and D-H parameters of industrial robot. Finally, compared with other calibration methods, it can be seen that the calibration method based on Fixed Axis-Invariant proposed in this paper can obtain better results. It can improve the absolute positioning accuracy of industrial robots to less than 0.28 mm, which can solve the problems of cumbersome industrial robot modeling and poor calibration effects.